1. Field of the Invention
The present invention relates to a moving picture expert group (MPEG) video decoder, and more particularly to an overflow processing for the MPEG video decoding system.
2. Discussion of the Related Art
Recently, digitalization of information has already been developed extensively. As a result, the picture compressing technology is becoming the major concern for multimedia. An MPEG is the international standard for coding the digital data of moving picture and is considered as the most effective compressing technology in the multimedia environment. The MPEG technology is widely used as the compressing algorithm in communication, broadcasting, game and the like including a digital TV.
The MPEG video compressing algorithm is based upon two elementary technologies. A motion estimation and compensation of the video in block units is used to reduce the temporal redundancy. Also, a discrete cosine transform (DCT) is used to reduce the spatial redundancy.
The DCT transformed video data signal is quantized into a set number of bits to reduce the total amount of data. The quantized data is processed through a variable length coding (VLC) which codes a frequently occurring value by a smaller number of bits and an occasionally occurring value by a larger number of bits, thereby reducing the entire number of bits. A motion vector of 16xc3x9716 block is obtained is transferred together with the DCT coefficient data.
A digital TV utilizing the MPEG technology includes a tuner, a demultiplexer, a video decoder and a monitor. The tuner selects one of a plurality of channel signals received through an antenna and demodulates the signals. The demultiplexer selects a desired program from a plurality of programs included in the selected channel and divides the program into packets of audio and video bit streams.
The video bit streams are coded at a variable rate by the VLC, temporarily stored in a video buffer and output to the video decoder at a fixed rate. The video decoder eliminates any overhead, such as various header data and a initial code, from the input video bit streams. The video decoder also restores the data to the original pixel value through a variable length decoding (VLD), an inverted DCT (IDCT), and a motion compensation using the motion vector. The restored pixel value is output to the monitor.
During the course of decoding, a temporary overflow may occur in the video buffer due to errors, particularly when the rate of data stored in the video buffer is faster than the rate of data read by the video decoder. In the background art, an overflow in the video buffer is regarded as a fatal error and the video buffer is reset. As a result, the video bit streams stored thus far in the video buffer are all erased and must be newly stored in the video buffer.
Thus, if an overflow occurs, the video buffer fails to store the video bit streams and the demultiplexer discards the video bit streams. If the video buffer is reset, the demultiplexer again stores the video bit streams in the video buffer. Meanwhile, the video decoder sits idle because of the discontinuity in the video bit streams output to the video decoder due to an overflow in the video buffer. Moreover, the video decoder does begin decoding until the sequence header is searched and found even though when the video bit streams are newly stored in the video buffer.
In the background art, whenever an overflow occurs in the video buffer, the video buffer is reset to erase all the video bit streams stored in the video buffer. In addition, the video decoder does not begin decoding until the sequence header is searched even though new video bit streams are stored again in the video buffer and input to the video decoder. For these reasons, the overflow causes a loss in several tens of frames of picture data.
Accordingly, an object of the present invention is to solve at least the problems and disadvantages of the related art.
An object of the present invention is to minimize losses of video bit streams in the overflow processing of a MPEG video decoding system.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purposes of the invention, as embodied and broadly described herein, a MPEG video decoding system includes a video buffer temporarily storing video bit streams compressed for decoding and outputting a signal indicative of an overflow if an overflow occurs; and a demultiplexer demultiplexing and storing the video bit streams in the video buffer, discarding the video bit streams without storing the bit streams if the signal indicative of overflow is input from the video buffer, and begin storing the demultiplexed video bit streams in the video buffer if a signal indicative of non-overflow is input from the video buffer.
In an another embodiment of an MPEG video decoding system according to the present invention also includes a video decoder which stops decoding until a code indicating a capability of performing normal decoding is detected if an error code is detected in the course of decoding, and outputting pixel data of pictures to a display portion.
In an another embodiment of an overflow processing method in an MPEG video decoding system according to the present invention includes the steps of indicating an overflow if an overflow occurs in a video buffer, discarding the demultiplexed video bit streams without storing them in the video buffer if a signal indicating an overflow is input from the video buffer, indicating a non-overflow when an overflow of the video buffer is eliminated, and begin storing the demultiplexed video bit streams in the video buffer when a signal indicative of non-overflow is input.